Synchronizing airplane engines



' D. E. BENCH ETAL SYNCHRONIZING AIRPLANE ENGINES Jan 6,1942.

Fil ed Feb. 23, 1939 Im/uxk 6r Davm E. Bane.

Js B,.VJ ma. Cm m. ms T M Patented 6, 1942 SYNCHBONIZING AIRPLANEENGINES David E. Bench and Melvin A. Crosby, Dayton, Ohio, minors to TheHydraulic Development Corp. Inc., Wilmington, Del., a corporation ofDelaware Application February 23, 1939, Serial No. 257,990

7 Claims.

This invention relates to apparatus for synchronizing airplane enginesalthough it will be apparent that it may be applied to the synchron-.which is adapted to be readily installed in airplanes. 7

It is another object of the invention to devise such a synchronizingapparatus which employs hydraulic means for synchronizing the severalairplane engines.

It is another object of the invention to provide a modificationof themain inventive thought wherein the only connections between the severalengines to be synchronized are hydraulic.-

This facilitates installation since it is possible for hydraulicconduits to be readily bent as is necessary to pass from one portion ofthe airplane to another.

It is another object of the invention to provide a synchronizing meansfor aircraft engines which employs differential means to control theseveral engines. 1 v

Still another object is to provide a synchronizing mechanism formultiple aircraft engines wherein the manual control for the pilot doesnot actuate the throttle -of any engine directly but acts indirectlythrough hydraulic and differential means to open the throttles of theseveral engines simultaneously and'in such manner that each engine isperfectly synchronized with each other engine. I

Referring to the accompanying drawing:

Figure 1 is a diagrammatic representation of one way in which thepresent invention may be adapted to the synchronization-oi. two airplaneengines;

Figure 2v is an enlarged sectional diagrammaticalview of throttlecontrolling means 5 and 5 ofFigure 1; and

Figure 3 is a diagrammatical view of the application of this inventionto the synchronization of three airplane engines. of Figure 3 may beemployed to synchronize any The apparatus number of airplane engines ormultiple prime;

movers, whereas apparatus of Figure 1 is parand associated shaft l4.

ticularly adapted to the synchronization of two engines only.

With reference to the accompanying drawing and particularly to Figure 1thereof, I and 2 represent the two airplane engines which are to beoperated synchronously one with the other. Engine l drives, by asuitable power take-off device, a shaft 1 at a speed which is in directproportion to the speed of engine I. Shaft 1 may be conveniently drivenby the cam shaft of engine I. Integrallyattached to shaft 1 is a bevelgear 8 which drives bevel gear 9 and associated shaft l0. Shafts 'I andIII are driven in the direct-ions indicated by the arrows thereon.

Engine 2 drives by a similar power take off device, a shaft II. Thisshaft H is conveniently driven from the cam shaft of engine 2 so that itrevolves at a speed directly proportional to the speed of engine 2 andat a speed which is related to the speed of engine 2 in the same manneras the speed of shaft I is related to the speed of engine I. Shaft ,II'has integrally attached thereto bevel gear l2 which drives bevel gear l3in the directions indicated by the arrows thereon. Consequently shaftsl0 and I4 rotate at the same relative speeds .with respect to the speedsof engines I and 2 respectively.

Shafts Ill and i4 operate a differential device generally designated asIs. Shaft I 0 has integrally attached thereto bevel gear l6, while shaftll has integrally attached thereto bevel ear l'l. Bevel gears l6 and ilengage spider gears l8 and 19 which are mounted on ring gear 20 in theusual manner. Ring ear 20 drives bevel gear 2| which is integrallyattached to shaft 22 which drives pump 4 23 designates the throttle rodof engine I while reference numeral 24 designates the throttle rod ofengine 2. 23 is a cylinder 5 and integrally attached to throttle rod 24is a similar cylinder 6. Cylinder 5 is shown in an enlarged view inFigure 2 and it is to be understood that cylinder 6 is similarlyconstructed. Connectingthe liquid end of cylinder 5 to pump 4 is aliquid conduit 25 and disposed between the liquid end'of cylinder 6 andobtain revolution of engines I and 2 at the desired speed. After settinghand lever 3 in a given position the synchronizing device willautomatically maintain engines I and 2 at the de Shafts H and I 4 rotateIntegrally attached to throttle rod These rods 21 and 28 are so disposedwith ref-.

erence to the pivot of lever 3 that movement of lever 3 in a givendirection functions to operate the throttles of engines I and 2 in asimilar manner. Thus, if lever 3 is pushed to the right, both rods 21and 28 draw away from engines I and 2 respectively and operate tosimultaneously close the throttles of said engines.

Cylinder will now be described and it is to be understood that cylinder5 is to be constructed in the same manner. Throttle rod 23 of engine Iis integrally attached to the cylinder portion of cylinder 5 so thatrelative motion of cylinder 5 with respect to engine I moves throttlerod 23 in the same fashion. Disposed within cylinder 5 is a slideablepiston 28 which is integrally attached to rod 21 leading from hand lever3. Disposed between the rear part 3| of the casing of cylinder 5 andpiston 25 is a yielding spring 32 which operates to push piston 25 tothe right so as to maintain the right hand portion of cylinder 5 filledwith liquid at all times. Conduit 25 from pump 4 is in liquid pressureengagement with the liquid chamber 33 of cylinder 5. 34 designates anair vent which allows air displaced from the left hand portion 35 ofcylinder 5 to make its exit from the cylinder and likewise allowsatmospheric air to enter into chamber 35 when piston 25 is moved to theright.

Figure 1 shows two engines which are not alike in characteristics. Thus,engine I tends normally to run at a lower speed than engine 2 with anequal throttle opening. The effect of this tendency of engine I willpresently be apparent.

The synchronizing action of the device shown in Figure 1 will now bedescribed. Assume that hand throttle lever 3 is in any given position asfor example in the position shown in Figure l and assume that engine 2is running faster than engine I. Shaft II will be driven correspondbedriven faster than shaft I0 and in the 0p- .posite direction.Accordingly due to the difierspeeds of shafts l4 and III. Rotation ofrin gear 25 causes corresponding rotation of pump shaft 22 which causesliquid to be pumped from cylinder 5 through conduits 25 and 25 intoliquid chamber'33 of cylinder 5. Since the position of rod 21 and ofpiston 29 is fixed by the setting of throttle controlling lever 3 theaction of pump 4 in pumping liquid into the liquid chamber 33 ofcylinder 5 will force cylinder 5 to the right carrying with it throttlerod 23 and opening the throttle of engine I and will suck cylinder 5 tothe right carrying with it throttle rod 24 and closing the throttle ofengine 2. Thus, engine I will be speededup and engine 2 willbe sloweddown until shafts I0 and I4 revolve at the same speed under whichcondition rotation of ring gear 25 and operation of pump 4 will cease.Should for anyreason engine 2 operate at a lower speed than engine I,shaft M will rotate at a correspondingly'lower speed than shaft I0 I andring gear 25 will thereupon be rotated in the same direction as shaft llcausing pump 4 ingly faster than shaft 1.. Shaft I4 will likewise topump liquid from cylinder 5 into the liquid chamber of cylinder 5thereby opening the throttle of engine 2 and closing the throttle ofengine I until equilibrium is once again established.

As liquid is pumped from one cylinder to the other, the engine fromwhose cylinder liquid is pumped will be slowed down while the engine towhose cylinder liquid is pumped will be speeded up. This dual actionresults in a very quick regaining of equilibrium after equilibrium hasonce been disturbed.

It will be apparent that pump 4 is of any suitable type which'is adaptedto pump liquid with either of its outlets acting as either an inlet oran outlet. Thus, it is a reversible pump and conduit 25, for example,may be said to be an inlet conduit as well as an outlet conduit andconduit 25 may be similarly-designated.

Referring now to Figure 3; 35, 31 and 38 represent three engines whichare to be operated synchronously. The throttles of these engines aredesignated as 35, 40 and H respectively.

' Reference numeral 42 designates an electric motor which is adapted tobe driven by battery 43. Motor 42 is of the variable speed-type and itsspeed may be varied within suitable operating limits by means ofrheostat 44. It is to be understood that motor 42 may be of anyvariable, speed type and that control of the speed of motor 42 may beattained in any manner. As illustrated, rheostat 44 would be placed inthe pilots cockpit and would be used by the pilot to control the speedsof the engines. By increasing the resistance of rheostat 44 the speed ofelectric motor 42 would be decreased and correspondingly, bydecreasingthe resistance of rheostat 44 the speed of motor 42 would beincreased.

Electric motor 42 drives'a liquid pump 45.'

Liquid pump 45 pumps liquid from tank 45 through inlet conduit 41 andoutlet conduit 48 through the several hydraulic motors 49, 50 and 5I.From hydraulic motor 5| a conduit 52 leads the liquid pumped through thecircuit to tank 46.

Hydraulic motors 49, 50 and 5| are of any suitable type which willoperate accurately and synchronously when liquid is passed therethroughat a given rate. These motors may be, for example, similar to'or thesame as meter devices employed .for measuring liquid in liquiddispensing devices such as gasoline pumps. By virtue of their beingconnected in series each of these motors receives the sameamount ofliquid in a given amount of time and by virtue of the accuracy withwhichmotors 49, and SI are constructed, their shafts 53, 54, and 55rotate at exactly the same synchronous speed.

Engine 35 drives, by any suitable power takeoff device, a shaft 55 in adirection opposite to that in which shaft 53 is driven. interposedbetween shafts 55 and 53 is a differential device designated generallyas 51.- This differential device may comprise bevel gears or frictiondiscs.

Differential 51 is constructed in the usual mandirection as shaft 53will cause corresponding rotation of pinion 55 which is drivinglyconnected with worm 55 and will cause the opening of throttle 35 onengine 34 until engine 35 drives shaft 56 at the same speed as shaft 53when Figure 3. If more than three engines are to be Engine :1 isprovided with a similar driven shaft 6|, differential device indicatedgenerally as 62, ring gear 63, pinion 64 and worm 65. The mechanisminterposed between engine 31 and hydraulic motor 50 operates in the samemanner as that described 'in connection with engine 36. Engine 38 issimilarly provided with a driven shaft 66, with a differentialdesignated generally as 61 interposed between shafts 66 and 55,,

with a ring gear 68, with a pinion 69 and with .worm 18, all of whichoperate in the same mancauses an opening of the throttle of engine 36. I

It will be apparent that connecting rod 14 which connects collar II withthe throttle rod of throttle 39 is pivoted at 13 and 15 so as to befreely rotatable with respectto collar 1| and the throttle rod ofthrottle 39. The construction of the throttle controlling mechanismemployed on engines 31 and 38 is similar.

In operation the device of Figure 3 functions as follows:

Assume that the engines are idling and that' the pilot wishes to bringthem up to speed. He

will increase the speed of electric motor 42 bymanipulating control 44.The increase in speed 'of motor 42 will cause a similar increase inspeed of pump 45. This will cause liquid to be pumped through thecircuit at a correspondingly increased speed. Hydraulic motors 49, 56and 5| will correspondingly and simultaneously increase in speed andshafts 53, 54 and 55 will likewise be driven at a higher speed and insynchronous relationship. Ring gears 58, 63 and 68 will thereupon becaused to rotate in the same direction as shafts 53, 54 and 55 and at aspeed corresponding to the difference in speeds between shafts 53, 54and 55 and shafts 56, 6| and 66 respectively. Pinions 59, 64 and 69 willthen be synchronized each additional'engine is provided with a hydraulicmotor, with a driven shaft and with a differential device which controlsits throttle, and the hydraulic motor or motors of the additional engineor engines are connected in series with the hydraulic motors portrayedin Figure 3.

The device portrayed in Figure 3 is unique in that the synchronizingmeans opens the throttles of all of the engines simultaneously and thatthe control placed in the pilots cockpit does not directly open thethrottle of any of the engines of the airplane.

While Figure 1 shows the use of bevel gears and Figure 3 shows the useof friction gears in the differential mechanism, it is to be understoodthat if desired, friction discs may be employed in the differential ofFigure 1 and bevel gears may be employed in the differentials of Figure3. It is to be understood that where a liquid is mentioned in thisspecification, any suitable non-compressible liquid such as 'oil or thelike may be employed as the hydraulic conducting .medium.

of Figure 1 may be connected to differential l5 by means of flexibleshafts. The use of such flexible shafts will facilitate location of thedifferential l5 andpump 4 in the pilot's cockpit or in the main body ofthe aircraft as where engines and 2 are located outwardly of the mainbody of the aircraft, as for example, in the wings thereof. 1

If desired the electric motor 42 of Figure 3 may be replaced with amanually controlled prime mover such as one of the engines of theairplane. In this way such a manually controlled engine would be amaster engine and its speed would controlthe speed of'the remainingengines by reason of pump 45 and the hydraulic motors disposed in seriestherewith. It will be understood that in using such a system, ofsynchronization any number of subsidiaryengines may be oper-' atedsynchronously with each other and with such a master engine.

It will be seen that by means of the invention described above, itispossible to accurately synchronize a plurality of airplane engines bymeans which are simple in construction and which result in absolutesynchronization of the several engines throughout their speed range. Itis to be understood that we intend to comprehend as within ,ourinvention such modifications as are necessary to adapt the same tovarying conditions and uses.

Having thus fully described our invention,

' Letters Patent, is:

it and the hydraulic motor shaft corresponding to it will operate thedifferential mechanism in such manner as to set the throttle of thatengine so as to operated: in perfect synchronism with the remainingengines.

Any number of engines may be synchronized perfectly by means of theinvention portrayed in 1. In a mechanism for synchronizing multipleprime movers, a variable speed motor driving a liquid pump, hydraulicmotors for each of said primemovers and arranged in series with saidliquid pump, a shaft driven by each of said prime movers at a speed inroportion to the speed of said prime mover, diff rential means disposedbetween said pump and said shaft, one side of which is driven by saidshaft and the other side of which is driven by said hydraulic motor, andmechanical means operable by saiddiiferential means andpositivelyconnecting the latter with the respective prime mover for controllingthe speed of each of said prime movers 2. In a mechanism forsynchronizing multiple prime movers, a liquid pump, a plurality ofhydraulic motors in series therewith, there being a hydraulic motor foreach prime mover, differential means associated with each of said primemovers and operable by the difierence in relative speeds of said primemovers and said hydraulic motors, and mechanical connecting meanspositively connecting a speed control member of each of said primemovers with the respective differential means for governing the speed ofeach of said prim-e movers.

3. In a mechanism for synchronizing multiple prime movers, an electricmotor, the control of the speed of said prime movers being obtainedindirectly by the control of the speed of said electric motor, a liquidpump driven by said electric motor, a hydraulic motor associated witheach of said prime movers, a shaft driven by each of said prime movers,a differential interposed between said shaft and the shaft of each ofsaid hydraulic motors. and mechanical means opera -ble by the differencein speed between said shaft driven by said prime mover and saidhydraulic motor and positively connecting said difierential with a speedcontrolling member of the respective prime mover to govern the speed ofsaid prime mover.

4. In a mechanism for synchronizing multiple prime movers, a variablespeed electric motor, a liquid pump driven thereby, a hydraulic motor inassociation with each of said prime movers and i arranged in series witheach other and with said pump, a differential interposed between each ofsaid prime movers an'd'each of said hydraulic motors, one side or saiddiflerential being driven by each of said prime movers and the otherside of each of said diflferentials being driven by said hydraulicmotors, and means driven by each of said differentials and positivelyconnected with the respective differential for varying the speed of eachof said prime movers.

5.'In a mechanism for synchronizing a plurality of prime movers, ahydraulic pump, manually speed-controlled means for driving said pump, aplurality of hydraulic motors in series with. said pump and driventhereby, a plurality of difierential means, each of which is driven byone of said motors and one of the prime movers to be synchronized, andmechanical means directly operated by said differential means andpositively connected with a speed control member of the respective primemover for controlling the speed of the prime mover with which it isassociated.

6. In a mechanism for synchronizing a plurality of prime movers, ahydraulic pump, means for driving said pump at a desired speed, a shaftdriven by one of the prime movers to be synchronized at aspeedproportionate to the speed thereof, a hydraulic motor driven by saidpump, a shaft driven by said hydraulic motor and at a speedproportionate to the speed of said pump, differential means operable bythe difference in speeds of said shafts,- a gear associated with eachprime mover and meshing with said differential means, and mechanicalmeans positively connecting said gear with a speed control member of therespective prime mover for controlling the speed of the prime mover withwhich it is associated.

'7. In a mechanism for synchronizing a plurality of internal combustionengines each having an adjustable control member for varying the fuelintake, a hydraulic pump, means for driving said pump at a desiredspeed, a plurality of hydraulic motors in series with said pump anddriven thereby, a plurality of differentials, each of said differentialsbeing driven by one 01 said motors and one or said engines to besynchronized, a gear associated with each engine and meshing with thedifferential pertaining thereto.

and mechanical means positively connecting said' gear with therespective control member for con- 1 trolling the speed of said enginewith which it is associated.

' DAVID E. BENCH.

MELVIN A. CROSBY.

